function y = sqrt_from_negative_num(arg_vec)

    y_vec = zeros(size(arg_vec));
    for i = 1:size(arg_vec, 1)
        arg = arg_vec(i);
        if (arg >= 0)
            y_vec(i) = sqrt(arg);
        else
            y_vec(i) = - sqrt(arg);
        end
    end
    y = y_vec;

end